FreeFlyer

FreeFlyer Key Features Expanded

Graphic User Interface (GUI)

FreeFlyer provides and easy-to-use and navigate Graphic User Interface with drag-and-drop functionality and "intellisense" for easy problem setup and output generation. Each run is controlled by the GUI-built "Mission Plan", which allows the user to set up each simulation or operations scenario in a time-ordered and human readable form. The Mission Plan is the user's mission timeline or "sequence of events". The GUI also allows rapid access to all assets being used for the simulation as well as specifying all output types, plots and reports. Through the GUI, the user can modify all assets, including all spacecraft, launch vehicle and associated hardware, ground stations and ground area targets,

FreeFlyer's user interface also provides wizards for quick set up of common mission design analysis such as orbit propagation and station coverage analysis. Also available through the GUI are demonstration mission plans and sample mission plans which exercise some of FreeFlyer's key functionality.

The user can also customize their own GUI pages using FreeFlyer's customizable user interface. The Customized User Interface allows users to simplify data input by building their own analysis-specific or mission-specific GUI pages. You can easily build GUI pages that allow access to only the parameters that you wish to change, without the need to recompile. This feature is extremely useful in spacecraft operations environments and in repeated analyses.

Integrated 2D & 3D Visualization

FreeFlyer comes complete with both 2D and 3D visualization for displaying simulation or operational data in real-time. FreeFlyer's 2D world map (or map view) can display 2D spacecraft, ground trace, ground station masking, ground area targets, ground regions and spacecraft sensor footprints. In 3D, several view options are available to the user, such as Celestial Sphere view, Globe view, Sensor view and Camera view. The Camera view allows the user to place a "camera" anywhere in 3-dimensional space, allowing the user to take a "snapshot" view from any angle. All views can be tailored to show as few or as many assets as desired, such as multiple spacecraft (orbit geometry, position and attitude), ground stations, three-dimension sensor or antenna patterns and masking, ground regions and moving parts.

Any combination of view, both 2D and 3D, can be preset or changed in real-time during any given simulation. FreeFlyer supports unlimited window tiling to allow multiple views (including reports and plots) of the same problem from different perspectives—all updated in real-time.

Spacecraft & Hardware Modeling

FreeFlyer supports full modeling of spacecraft for complete and accurate mission design. All spacecraft physical properties such as mass, center of mass, inertial and aerodynamic properties are available for user input and manipulation. FreeFlyer models spacecraft hardware such as complex sensors and antennas with irregular patterns and obscuration masking. Sensors can also be set up to actively track targets.

FreeFlyer models a variety of tank types and an unlimited number of tanks and thrusters. Both simple and complex propulsions systems (including bi-propulsion) with mass depletion can be modeled. FreeFlyer also models ground stations, ground station masking, transceivers and ground regions.

Coverage & Visibility Analysis

FreeFlyer has optimum flexibility when it comes to visibility and access analysis. Pass and access data (times, angles, distances, rates) can be computed and displayed in real-time for inter-visibility between any assets or groups of assets contained in each simulation or operational scenario. Each access calculation can be controlled using field-of-view constraints such as sensor obscuration or ground station masking. Revisit statistics, percent coverage (ground area or ground station) and sun/shadow times are all easily and rapidly calculated, displayed and reported.

Sensor coverage to ground targets or other spacecraft targets is easily analyzed. Coverage analysis can be calculated based on line-of-sight on based on spacecraft or sensor attitude (including sensor or ground masking).

Spacecraft Attitude Modeling

FreeFlyer provides several flexible options for defining spacecraft attitude. Users can define attitude by attitude matrix, quaternions, Euler Angles, or spinning (right ascension and declination, spin rates). Users can apply attitude rates and both read and create attitude history files. FreeFlyer offers users the flexibility to use the FreeFlyer resident attitude history file (AHF) format or to read and write an ASCII or Binary attitude history file in any user-specified format. FreeFlyer also has the ability to read in Satellite Tool Kit (STK) formatted AHF files.

FreeFlyer has many resident functions for matrix manipulation and Euler angle conversion, but also provides users with a built-in MATLAB connection, allowing users to easily call MATLAB and return data back to FreeFlyer.

There are several pre-defined attitude reference frames available to the user such as Geodetic, Local Vertical Local Horizontal (earth-pointing) and Mean of J2000 Earth Equator; however, FreeFlyer's Custom Coordinate System feature allows users to define any coordinate system. One the user defines the customer coordinate system (using vectors), the coordinate system can then be attached to a spacecraft, launch vehicle or sensor.

Dynamic Real-Time Processing

All FreeFlyer simulations or operational scenarios are controlled by the "Mission Plan." The Mission Plan is your mission timeline or "sequence of events." The Mission Plan is set up via the GUI and can be edited via the GUI or externally. FreeFlyer is dynamically propagated (not batch processed). This means that mission plans can be altered and continued through the course of a single run. All orbit and attitude calculations occur at each integration step. All reports, plots, 2D and 3D views are created in real-time during the simulation, giving users immediate feedback. FreeFlyer's dynamic nature reduces wasted time and design cycles by allowing users to stop a run at any point needed—as opposed to having to let each run finish before being able to see and interpret results. Users may, if they desire, create a report or ephemeris of orbit and attitude data and then at some later date, read the ephemeris file back in to generate reports and plots.

Logic Control & Full-Featured Scripting Language

All FreeFlyer functionality can be controlled via logic control commands such as For, If, While, Pause, Stop, Achieve and Vary. This flexibility allows for looping, branching and decision-making based on any calculated parameter at each/any integration step. This feature allows for the easy set up of trade space analysis, parametric studies and the automation of routine flight dynamics tasks. Multi-variant analysis can be easily performed within a single run. Logic control allows spacecraft components such as sensors to be turned on and off based on any set of conditions such as contact parameters or events such as sun/shadow or beta angle constraints.

The flexibility of logic control is further enhanced by a full-featured, intuitive scripting language. Freeflyer's versatile scripting language allows users to implement any user-specified algorithm without the need to compile. If you can script it, FreeFlyer can do it. FreeFlyer's powerful scripting language discriminates it from any other COTS space mission design software available today.

Unlimited Customizable Reports & Plots

FreeFlyer allows unlimited customizable reports and plots to be generated on any data calculated. With over 1300 predefined orbit parameters available (plus unlimited user-defined variables), the data reporting and plotting capabilities are infinite.

Built-in Interfaces

FreeFlyer offers multiple external interface features that allow users the flexibility to connect and exchange data with other systems. The MATLAB interface allows users to exchange data with MATLAB at every FreeFlyer integration step. This allows users who have algorithms already in MATLAB to attach and use these during a FreeFlyer run and gain the full flexibility of FreeFlyer's output functionality to display data. This feature is also extremely useful for those who have proprietary or mission-unique attitude or control laws already written in MATLAB.

The TCP/IP socket interface allows FreeFlyer to connect and share data with other applications. The socket interface can work in conjunction with the Database interface when users need to read in spacecraft data from a database that is resident on another machine. In operational scenarios, the database interface allows data from other ground system components to automatically populate FreeFlyer, thus minimizing human error.

While FreeFlyer has many pre-defined file formats, the File Interface allows users the ultimate in flexibility when reading and writing proprietary or mission-specific formatted files. The file interface allows users to custom define any ASCII or Binary file format. Once defined, the user can read, write, or edit the custom formatted file.

Orbit Determination

FreeFlyer offers robust orbit determination functionality with two computational engines; Extended Kalman filter (with optional smoother used concurrently) and batch least squares. Full-state and covariance matrices are calculated and output at each integration step in user-defined formatted ASCII reports. User selectable solve-for parameters include orbit states, drag, solar radiation pressure, ground station geodetic biases, and measurement biases. Data types include ground-based measurements (range, range rate, angles), TDRS-based measurements (one-way Doppler, two-way range, two-way Doppler), GPS measurements (position only, velocity only, position and velocity). Measurement modeling includes tropospheric correction, ionospheric correction and light-time correction.

Orbit data can be input and output via ASCII or Binary data files, ODBC-compliant database or TCP/IP socket. FreeFlyer supports the following pre-defined formats: ASCII, UTDF (TDRS UTDF), DSN, GPS, CERES. However, custom user-defined formats are also supported via FreeFlyer's File Interface.

FreeFlyer also generates simulated tracking data in the above listed formats for use in training and orbit determination error analysis.

Maneuver Analysis, Planning & Calibration

FreeFlyer supports high-precision modeling and analysis for maneuver planning, ascent planning, trajectory optimization and calibration. Both impulsive and finite maneuvers are modeled. Users can build precise models of spacecraft propulsion systems through definitions of tanks and thrusters attached to each tank. The performance, thrust scale factor, duty cycle information and valve status for each thruster is fully modeled to give an accurate representation in either pressure-regulated or blow-down configurations. Complex propulsion systems, such as bi-propellant, are also modeled. For finite maneuvers, fuel mass depletion and mass remaining are integrated during the maneuver using the ideal gas law and mass flow rate equations.

Targeting for maneuvers is handled by a differential corrector that handles standard square and non-square problems. A common use would be to target on the time and duration of a maneuver to achieve a desired orbital state. A standard detailed maneuver burn report is automatically generated for each maneuver performed. Users can also customize the maneuver output report to any level of detail and precision desired.

FreeFlyer's maneuver capability is unmatched due to its flexibility and accuracy. It is used daily by NASA to plan and perform all maneuvers for the EOS series of spacecraft (EO-1, Landsat-7, Aqua, Aura, Terra).

Advanced Analyses

FreeFlyer provides solutions to even the most complex flight dynamics challenges, including:

• Maneuver Planning and Optimization
• Ascent Planning and Optimization
• Spacecraft Propulsion System Sizing and Calibration
• Frozen Orbit Control
• Automated Orbit Control
• Formation Flying
• Constellation Design and Optimization
• Monte Carlo Analysis
• Automated Parametric Studies
• Collision Avoidance and Conjunction Analysis